Checking the Devices

Switches, appliances, and fixtures test a bit differently than receptacles. The first three are tested for continuity and power and require both testing tools. A continuity tester will indicate whether the circuit’s pathway within the switch has any breaks in it from metal fatigue. It also checks other appliances and fixtures for similar breaks. Let’s start with testing for a switch.
Follow these steps to test a switch for power:

1. With the switch off, touch one of the voltage tester’s probes either to the bare end of the ground wire (the inside of the wire nut holding the neutral wires together) or, if it’s a metal box, to the side of the box.
2. Place the other probe against each black wire either at the terminal screw or at the back-wired slot.
3. The bulb should light up for at least one of the hot wires, the line wire coming from the panel or fuse box. If the tester does not light up for either black wire, the problem is somewhere in the circuit between the panel and the device. (Go to step 4 if it does light up.)
4. Turn the switch on and check the other black wire, which is the load conductor. If the bulb on the tester does not light up, the switch is bad and needs to be replaced.
5. If both black wires show current passing through them, recheck the fixture and the appliance because the problem is not with the switch.
6. Note: In some older homes with knob-and-tube wiring, the neutral wire has been switched and used as a “hot” conductor. This makes the task of troubleshooting much more difficult. If you have any questions or concerns while testing, call an electrician.